Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>

using namespace std;


#define MAXN 51
int dx[4] = {1,  0, -1,  0};
int dy[4] = {0, -1,  0,  1};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string a[MAXN];
  int h, w, black = 0;;
  cin >> h >> w;
  for (int i = 0; i < h; ++i) {
    cin >> a[i];
    for (auto &c : a[i]) {
      black += c=='#';
    }
  }
  queue<pair<int, pair<int, int>>> q;
  q.push({1, {0, 0}});
  int ans = -1;
  while (!q.empty()) {
    auto nxt = q.front();
    q.pop();
    int i, j;
    tie(i, j) = nxt.second;
    if (i==h-1 && j==w-1) {
      ans =  h*w-black-nxt.first;
      break;
    }
    for (int di = 0; di < 4; ++di) {
      int I = i+dx[di];
      int J = j+dy[di];
      if (I<0 || I>=h || J<0 || J>=w || a[I][J]=='#') continue;
      a[I][J] = '#';
      q.push({nxt.first+1, {I, J}});
    }
  }
  cout << ans << endl;
  return 0;
}